Medical device employing liquid crystal block copolymers and method of making the same

ABSTRACT

A medical device, at least a portion of which is formed from a polymer composition including at least one liquid crystal block copolymer having at least one A block and at least one B block wherein the A block is a liquid crystal polymer block formed of repeating units comprising mesogenic groups and the B block is a non-liquid crystal polymer block.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 11/353,606 filed Feb. 14, 2006, hereby incorporatedby reference.

FIELD OF THE INVENTION

The present invention relates to the field of insertable and/orimplantable medical devices, particularly to balloon catheter assembliesand components thereof.

BACKGROUND OF THE INVENTION

It is known to use liquid crystal polymers (LCPs) in combination withthermoplastic polymers, i.e. matrix polymers, for use in the manufactureof insertable and/or implantable medical devices such as catheterassemblies and components thereof such as inflatable medical balloonswhich can be disposed at the distal end of a balloon catheter assembly.For example, see commonly assigned U.S. Pat. Nos. 6,977,103, 6,905,743,6,730,377 and 6,284,333. See also U.S. Pat. Nos. 6,596,219, 6,443,925and 6,325,780 to Schaible.

Liquid crystal polymers are known to phase separate from commonly usedthermoplastic polymers into multiphase polymer compositions. Forexample, see U.S. Pat. Nos. 5,248,305 and 5,156,785 to Zdrahala.

Compatibilized blends of LCP and thermoplastic polymers have been foundsuitable for use as medical device balloon materials. See for examplecommonly assigned U.S. Pat. No. 6,242,063.

It would be desirable to have a liquid crystal polymer material or blendusing a liquid crystal polymer material which has increasedcompatibility over other previous LCP/polymer blends which could beemployed in the formation of medical devices, particularly in themanufacture of catheter assemblies or components thereof.

The art referred to and/or described above is not intended to constitutean admission that any patent, publication or other information referredto herein is “prior art” with respect to this invention. In addition,this section should not be construed to mean that a search has been madeor that no other pertinent information as defined in 37 C.F.R. §1.56(a)exists.

Without limiting the scope of the invention a brief summary of some ofthe claimed embodiments of the invention is set forth below. Additionaldetails of the summarized embodiments of the invention and/or additionalembodiments of the invention may be found in the Detailed Description ofthe Invention below.

SUMMARY OF THE INVENTION

The present invention relates to polymer compositions useful in theformation of medical devices which include at least one liquid crystalblock copolymer having at least one A block and at least one B block.

The A block, which may also be referred to herein as the mesogenic(liquid crystal) block, may include any suitable repeating unit, therepeating unit having mesogenic groups. Any suitable mesogenic repeatingunit may be employed herein.

In some embodiments, the A block has at least one aromatic group pereach mesogenic repeating unit and more suitably the A block has at leasttwo aromatic groups per each mesogenic repeating unit.

In other embodiments, the mesogenic repeating unit may includefluorocarbon chains. Suitably, the fluorocarbon chain includes at leasteight fluorocarbon groups, —(CF₂)₈—. A spacer may also be incorporatedin the chain. In some embodiments the spacer includes three or lessmethylene, —CH₂ groups.

The B block may be formed of any suitable repeating unit which does notinclude mesogenic groups, i.e. the B block is a non-liquid crystalpolymer block.

In some embodiments, the B block is aliphatic. Suitably the B block hasless than 10% aromaticity by weight of the B block, more suitably lessthan 5% aromaticity by weight of the B block and most suitablysubstantially no aromaticity.

In other embodiments, the B block may be aromatic. In some embodiments,the B block is formed of styrenic units.

The polymers may be formed using conventional reaction techniques suchas condensation reactions, chemical modification of precursor polymerssuch as through addition reactions, sequential addition of a first blockto a second block, anionic or cationic polymerization, free radicalpolymerization, coupling end-functionalized prepolymers, ring openingmetathesis polymerization, group transfer polymerization, etc., as willbe described in more detail below.

These polymers may be employed alone, or in combination with otherpolymers.

The polymers find particular utility in the formation of medical devicessuch as catheter assemblies and components thereof, including, forexample, shafts, tips, manifolds and balloons.

These and other aspects, embodiments and advantages of the presentinvention will become immediately apparent to those of ordinary skill inthe art upon review of the Detailed Description and Claims to follow.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific embodiments of the invention. Thisdescription is an exemplification of the principles of the invention andis not intended to limit the invention to the particular embodimentsillustrated.

All published documents, including all US patent documents, mentionedanywhere in this application are hereby expressly incorporated herein byreference in their entirety. Any copending patent applications,mentioned anywhere in this application are also hereby expresslyincorporated herein by reference in their entirety.

The present invention relates to polymer compositions useful in theformation of medical devices or at least a portion of a medical device.The polymer compositions include at least one liquid crystal blockcopolymer having at least one A block and at least one B block.

The A block is formed of mesogenic (liquid crystal) repeating units. Asused herein, the term “mesogen” shall be used to refer to thosestructural groups which impart liquid crystal properties, such asstiffness and restriction to rotation, to the polymer. The term“mesogenic unit” as employed herein, shall be used to refer to anypolymer repeating units having a mesogen. Mesogenic groups may includeother structure groups, as well as spacers such as methylene groups, andlinking groups.

Polymer repeating units include backbone portions which includinglinking groups and typically an intermediate linear or cyclic structuretherebetween. Repeating units often include one or more groups pendentto the backbone polymer chains.

The mesogenic repeating unit of the present application may be said toinclude both a mesogenic portion and a spacer. Spacers are typicallyflexible and often include methylene (—CH₂—) groups. Flexible spacershave been found to be advantageous when inserted between the polymerbackbone and the mesogenic side group, for example, to separate themotion of the polymer backbone. See, for example, X. Han et al.,“Synthesis and Characterization of Side-Chain Liquid CrystallinePoly[1-({[4-cyano-4′-diphenyl)oxy]alkyl}oxy)2,3-epoxypropane]”,Macromolecular Chemistry and Physics, Vol. 205, pp. 743-751 (2004). Themesogenic repeating units of the A block can be attached together insuch a way that the mesogen portion of the mesogenic repeating unitforms a part of the backbone (main chain liquid crystal polymerstructure), or they may be attached together in such a way that themesogen is attached to the polymer backbone as a pendant group (sidechain liquid polymer structure). Examples of mesogenic repeating unitsemployed in main chain liquid crystal polymers wherein the mesogenportion of the mesogenic repeating unit forms a part of the backbone ishydroxynaphthoic acid, and poly(p-phenyleneterephthalate).

Liquid crystals exhibit a phase of matter which exists between acrystalline (solid) and an isotropic (liquid) phase, that has propertiesbetween those of a conventional liquid, and those of a solid crystal.For instance, a liquid crystal (LC) may flow like a liquid, but have themolecules in the liquid arranged and oriented in a crystalline way. Itis the mesogen of the mesogenic repeating unit which induces thestructural order, rigidity and necessary restriction on movement thatallows the polymer to display these liquid crystal properties. Themesogen is typically made up of one or more aromatic rings. Suitably,each mesogenic repeating unit has at least one aromatic group per eachrepeating unit, and more suitably each mesogenic repeating unit has atleast two aromatic groups per each repeating unit.

The B block may be either a hard block or a soft block, providing thatit is not formed of mesogenic repeating units. The block copolymer mayalso be of a multiblock variety including C blocks, D blocks, etc. The Cblock and the D block may be either be non-liquid crystal blocks orliquid crystal blocks. For example, in the case of an ABC blockcopolymer, the A block may be formed of a first mesogenic repeatingunit, the B block may be formed of a non-mesogenic repeating unit, andthe C block may be formed of a second mesogenic repeating unit differentthat the first mesogenic repeating unit. In some embodiments, the Bblock is immiscible with the A block.

The block copolymers may be of the general formula A-B diblock, A-B-Atriblock and B-A-B triblock, polyblock copolymers of the formula(A-B)_(n) where n is 1 to 20, A(B-A)_(n) and B(A-B)_(n) where n is 2 to20, A-B-A-B-A pentablock, multiblock polymers such as A-B-C, A-C-B orBAC triblock copolymers, B-(A-B-C)_(n) wherein n is 3 to 20, A-B-C-Dmultibock copolymers, random block copolymers and alternating randomblock copolymers, etc.

Furthermore, branched architecture block copolymers including H-type,T-type, stars (including symmetric and heterobranched stars), combs,brushes, dendrons/hyperbranched, etc. may be employed herein.

Individual polymer blocks of a block copolymer are often referred to inthe art as being either a “hard block” or a “soft block”, and may bedefined in terms of its Tg, the hard block having a relatively highglass transition temperature (Tg) and the soft block having a relativelylow Tg. A hard block, for example, may be considered as having a high Tgof greater than room temperature or greater than about 25° C., forexample, while a soft block may be considered as having a Tg of lessthan room temperature or less than about 25° C. However, this isintended for illustrative purposes only. For example, see U.S. Pat. No.6,790,908, the entire content of which is incorporated by referenceherein, wherein the stiff block is defined as having a glass transitiontemperature of greater than about 50° C., and preferably greater than100° C.

The A block, which may also be referred to herein as the mesogenicblock, may include any suitable mesogenic repeating unit. In someembodiments, he mesogenic repeating unit has at least one aromatic groupper unit, and more suitably the mesogenic repeating unit has at leasttwo aromatic groups per unit. The A block of the liquid crystal blockcopolymer is characterized by mesogenic repeating units which canprovide the liquid crystal block copolymer with stiffness resulting fromrestriction on rotation caused by steric hindrance and resonance. Forexample, aromatic ring(s) can provide both steric hindrance andresonance. Some mesogenic repeating units may include both aromatic andaliphatic rings.

The A block may contain any number of repeating units up to about 50.

Suitably, the mesogenic block has an axial ratio, defined by the lengthof the molecule divided by the diameter (x=L/d), of at least three. Thisaxial ratio provides the mesogenic block with rod-like characteristics.

The mesogenic block can be formed using a variety of techniquesincluding, but not limited to, polymerization of mesogenic monomericrepeating units, addition of mesogenic side chain groups to otherwisenon-mesogenic blocks followed by sequential addition of the mesogenicblock to a non-mesogenic block, chemical modification of a non-mesogenicblock copolymer by addition of mesogenic side chain groups, etc.

A variety of methods can be employed in the formation of the LCP blockcopolymers discussed herein and some of which are discussed in moredetail below. Conventional condensation reactions are commonly employed,as well as chemical modification of a precursor polymers such as throughaddition reactions, anionic and cationic polymerization, free radicalpolymerization, ring opening metathesis polymerization, couplingend-functionalized pre-polymers, group transfer polymerization,sequential sequential addition of a first block to a second block. See,for example, P. Gopalan et al., “Rod-Coil Block Copolymers: An IterativeSynthetic Approach via Living Free-Radical Procedures,” Journal ofPolymer Science: Part A: Polymer Chemistry, Vol. 41, pp. 3640-3656(2003), Hakemi, H., “On the miscibility of liquid crystalline polymers,”Polymer, Vol. 41, pp. 6145-6150 (2000), each of which is incorporated byreference herein in its entirety.

Condensation reactions are very common in the preparation of LCPcopolymers. Condensation often involves first synthesizing theend-blocks and mid-blocks and subsequently coupling of theend-functionalized prepolymers.

Alternating and random block copolymers have been prepared usingcondensation reactions. See U.S. Pat. Nos. 3,778,410 and 3,804,805, theentire contents of which are incorporated by reference herein.

ABA triblocks may also be prepared using condensation techniques. See,for example, B. L. Rivas et al., “Synthesis and Characterization ofBlock Copolymers from Poly(p-benzamide) and Poly(propylene glycol),”Macromolecular Chemistry and Physics, Vol. 202, pp. 1053-1059 (2001).

However, it should be noted that for LC block copolymers formed usingcondensation mechanisms, some prepolymers may be more suitable for useas end blocks than others due to reactive non-equivalency of the endgroups. Suitably, for a prepolymer to act as an effective end-block, oneend of the polymer chain should be non-reactive, while the other endshould be readily reactive to the endgroups of the other chain. Forexample, poly(1,-4-phenylene terephthalate) may be less suitable for useas compared to poly(4-benzoate) in formation of LC block copolymers. Anexample of a condensation polymerization which produces an AB-typecondensation polymer and involves a single monomer with two types ofreactive end-groups, i.e. 4-hydroxybenzoic acid, or 4-aminobenzoic acid,which yields a condensation product that has endgroups which havenon-equivalent reactivity is described by B. L. Rivas et al., “Synthesisand Characterization of Block Copolymers from Poly(p-benzamide) andPoly(propylene glycol),” Macromolecular Chemistry and Physics, Vol. 202,pp. 1053-1059 (2001).

Another technique which also may be employed in the formation ofcondensation block copolymers includes the use of two or more2,2′,6′,2″-terpyridine-substutitued prepolymers coordinating to a singletransition metal center to form block copolymers.

A variety of suitable mesogenic repeating units find utility in theformation of the A block of the liquid crystal block copolymer.

Classes of aromatic structural groups useful in the formation of mainchain mesogenic repeating units include, but are not limited to,aromatic dicarboxylic acids, aromatic hydroxycarboxylic acids, aromaticaminocarboxylic acids, diphenols, and aminophenols, for example.

Examples of useful aromatic dicarboxylic acids include, but are notlimited to, 1,4-naphthalenedicarboxylic acid,1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,diphenyl-4,4′-dicarboxylic acid, diphenyl-3,3′-dicarboxylic acid,diphenoxyethane-4,4′-dicarboxylic acid, diphenyl ether-4,4′-dicarboxylicacid, methylterephthalic acid, methoxyterephthalic acid,chloroterephthalic acid, 4-chloronaphthalene-2,7-dicarboxylic acid,1,3-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid,1,7-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid,diphenyl-3,4′-dicarboxylic acid, diphenyl ether-3,4′-dicarboxylic acid,4-methylisophthalic acid, 5-methylisophthalic acid, diphenylether-4,4′-dichloro-3,3′-dicarboxylic acid and iso- and terephthalicacid.

Examples of useful aromatic hydroxycarboxylic acids include, but are notlimited to, 4-hydroxy-3-methylbenzoic acid, 4-hydroxy-3-phenyl-benzoicacid, 4-hydroxy-2-ethylbenzoic acid, 3-chloro-4-hydroxy-benzoic acid,4-hydroxy-3-methoxybenzoic acid, hydroxylbenzoic acid including4-hydroxybenzoic acid and 3-hydroxybenzoic acid, hydroxynaphthoic acidincluding 6-hydroxy-2-naphthoic acid, etc.

Examples of useful diphenols include, but are not limited to,hydroquinone, t-butylhydroquinone, bromohydroquinone,chlorohydroquinone, methylhydroquinone, ethylhydroquinone,phenylhydroquinone, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenylether, 4,4′-dihydroxydiphenylethane, 4,4′-dihydroxydiphenoxyethane,3,5′-dihydroxybiphenyl, 4-hydroxy-4′-carboxybiphenyl,3,5′-dihydroxydiphenyl ether, naphthalene, dihydroxynaphthaleneincluding 1,4-, 1,5- and 2,6-dihydroxynaphthalene, for example,4-methoxy-2,6-dihydroxynaphthalene, 1,3-dihydroxynaphthalene,1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene,2,7-dihydroxynaphthalene, 2,5-dichloro-1,6-dihydroxynaphthalene,4-methoxy-2,7-dihydroxynaphthalene,2,2′-dimethyl-4,4′-dihydroxybiphenyl,3,3′,5,5′-tetramethyl-4,4′-dihydroxybiphenyl,3,5′-dimethoxy-4,4′-dihydroxydiphenyl ether,1,2-(2-chloro-4-hydroxyphenoxy)-ethane resorcinol,3,4′-dihydroxybiphenyl, 3,4′-dihydroxydiphenyl ether,3,4′-dihydroxydiphenoxyethane, 4-chlororesorcinol, 4-bromoresorcinol,4-methylresorcinol, 4-phenylresorcinol, 4-ethoxyresorcinol, etc.

Examples of aromatic aminocarboxylic acids include, but are not limitedto, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid,4-chloroanthranilic acid, 5-chloroanthranilic acid,3-amino-4-chlorobenzoic acid, 4-amino-3-phenyl-benzoic acid,4-amino-3-methoxybenzoic acid, 4-amino-3-phenoxybenzoic acid,6-amino-5-chloro-2-naphthoic acid, 6-amino-5-methyl-2-naphthoic acid and6-amino-5-methoxy-2-naphthoic acid, etc.

Examples of aminophenols include, but are not limited to, 3-aminophenol,5-amino-2-chlorophenol, 4-aminophenol, 3-amino-2-methylphenol,3-amino-4-methylphenol, 5-amino-1-naphthol, 6-amino-1-naphthol,8-amino-2-naphthol, 6-amino-2-naphthol and 4-amino-1-hydroxy-biphenyl,etc.

Other mesogenic repeat units not specifically recited herein can beemployed. For example, other dihydroxy biphenyls, dicarboxy biphenylsand diamino biphenyls, not specifically recited herein may also findutility in the formation of the LC block copolymers disclosed herein.

Other groups which may be included in a main chain mesogenic repeatingunit include paraphenylene (—Ar—) wherein Ar represents an aromaticring, as well as substituted paraphenylenes such aspara-diacetoxyphenylene (—CH₂COOCH2—Ar—CH₂COOCH₂—). Meta-phenylene mayalso be employed in the mesogenic repeating unit as well.

Other combinations of such groups which may produce mesogenic repeatingunits may also be incorporated into the repeating unit in the LC blockof the LC block copolymer. For a discussion of these structural groups,see for example, U.S. Pat. Nos., 4,663,422, 5,017,304 and 5,030,703 fora discussion of such structural units, each of which is incorporated byreference herein in its entirety. See also U.S. Pat. Nos. 4,238,599,4,801,677, 5,173,562, each of which is incorporated by reference hereinin its entirety, for further examples of suitable mesogenic units.

Other suitable mesogenic repeating units include those of the followinggeneral formula:

[-A-Y—X-Z-]_(m)

wherein X can be (CH₂)_(n) wherein n is an integer from about 2 to about10, m can range from about 2 to about 50, Y and Z can each independentlybe —COO or —CONH or can be a single bond between two carbon atoms, and Acan be p-phenylene, 1,4-naphthylene, 2,6-naphthylene or 1,5-naphthylene,monosubstituted phenylene with methyl, chloro or phenyl substitution,—ArCH═CHAr— wherein AR is a phenyl ring, —Ar—COOAr—, —Ar—CONHAr—, or—Ar—OOC—Ar—COO—AR—, etc. For a discussion of such mesogenic repeatingunits, see U.S. Pat. No. 4,952,334, the entire content of which isincorporated by reference herein.

Another specific example of a suitable aromatic mesogenic repeating unithas the structure —Ar—CO—NH—Ar—NH—CO—Ar—.

Other suitable mesogenic repeating units which can be employed hereinare described by Ober et al. in “Liquid Crystal Polymers. V.Thermotropic Polyesters with Either Dyad or Triad Aromatic EsterMesogenic Units and Flexible Polymethylene Spacers in the Main Chain,”Polymer Journal, Vol. 14, No. 1, pp. 9-17 (1982) and have the followingstructure:

—[—OArCOO(CH₂)_(n)OCOArOCOArCO—]—_(x)

wherein Ar represents phenyl with para-bond sites, n may range fromabout 2 to about 10, and x can range from about 2 to about 50. Thesemesogenic units can be characterized as aromatic ester mesogenic unitscomprising three linearly-aligned aromatic rings.

The type of mesogenic repeating unit represented by the formula above,wherein Ar represents phenyl with para-bond sites, n is an integer offrom about 2 to about 10, and x is an integer of from about 5 to about15, is described in U.S. Pat. No. 5,508,338, the entire content of whichis incorporated by reference herein.

Other specific examples of suitable mesogenic repeating units includepoly(hydroxynaphthoic acid) (—O—ArAr—CO—, wherein ArAr is two fusedbenzene rings) and poly(p-phenyleneterephthlate) (—O—Ar—OOC—Ar—CO—).

Another specific example of a suitable LC block employs a combination ofhydroxybenzoic and hydroxynaphthoic acid and has repeating units of theformula —[—O—AR—CO—]_(x)—[—O—ArAr—CO—]_(y)— wherein x and y are positivenumbers of 1 or more, for instance, x and y may vary independently fromabout 1 to about 50, and suitably about 1 to about 25. In someembodiments x=y=1 and in other embodiments x≠y. See, for example, U.S.Pat. Nos. 6,552,127, 6,054,537, 5,869,574, 5,767,198 and 5,750,626, eachof which is incorporated by reference herein in its entirety.

Another example of a mesogenic unit formed using a combination includesthat shown in U.S. Pat. No. 4,912,193, the entire content of which isincorporated by reference herein, employing a combination of p-hydroxybenzoic acid, 4,4′-dihydroxy biphenyl, terephthalic acid, andisophthalic acid. The above lists are intended for illustrative purposesonly and not as a limitation on the scope of the present invention.

Mesogen substituted (meth)acrylates, isocyanates, styrenic monomers, anddiene monomers such as isoprene and butadiene, can also be employed inthe formation of LCP block copolymers as disclosed herein.

Liquid crystal polymers having mesogenic acrylate repeating units findutility herein. One example of an acrylate mesogenic repeating unitwhich results in a side chain liquid crystal polymer structure is anacrylate repeating unit having the following structure:

Another example of a suitable (meth)acrylate based mesogenic repeatingunit which results in a side chain liquid crystal polymer structure isthe following:

Another example of a mesogenic (meth)acrylate based monomer is6-(4-methoxy-azobenzene-4′-oxy) hexyl methacylate. This monomer is usedin the formation of diblock and triblock copolymers as described in Heet al., “Synthesis of side-chain liquid-crystalline homopolymers andtriblock copolymers with p-methoxyazobenzene moieties and poly(ethyleneglycol) as coil segments by atom transfer radical polymerization (ATRP)and their thermotropic behavior,” Journal of Polymer Science Part A:Polymer Chemistry, Vol. 41, Issue 18, pages 2854-2864 (2003).

A specific example of an LCP block copolymer formed using a(meth)acrylate monomer modified with mesogenic side chains is disclosedin Gomes et al., “Synthesis of block and graft copolymers containingliquid-crystalline segments,” Polymer International, Vol. 48, pages713-722 (1999. In this example, non-LCP block or B block is polystyrene.The LCP block, having a Tg of well below 25° C. forms the soft block ofthe block copolymer while the polystyrene forms the hard block. The LCPblock copolymer can be formed using any of a variety of methodsincluding, for example, chemical modification ofpoly[styrene-co-tert-butyl acrylate]. In a specific example,poly[styrene-block-(tert-butyl acrylate] copolymer may be synthesized bya living anionic block copolymerization technique, followed by acid-baseneutralization of the acrylate with metal alkoxides or metal hydroxides,and subsequent esterification of the ionomer with a hydroxy-terminatedmesogen source such as HO(CH₂)₄OArAr.

LCP block copolymers which find utility herein may be formed with(meth)acrylate based monomer repeating units using controlled freeradical polymerization, specifically ATRP techniques, to form LCP blockcopolymers. See P. Ravi et al., “New water soluble azobenzene-containingdiblock copolymer: synthesis and aggregation behavior,” Polymer, Vol.46, pp. 137-146 (2005):

A triblock copolymer formed of rubber midblocks of poly(n-butylacrylate) and LCP endblocks formed of azobenzene modified (meth)acrylaterepeating units in another example of an LCP block copolymer havingutility herein. Such polymers are described in Cui et al., “PhotoactiveThermoplastic Elastomers of Azobenzene-Containing Triblock CopolymersPrepared through Atom Transfer Radical Polymerization,” Macromolecules,Vol. 37, pp. 7097-7104 (2004). Particular polymers have the followinggeneral structure:

where m and n are positive numbers indicative of the starting ratios ofthe respective monomers employed in the synthesis of the polymer. Analternative structure which may be employed in the present invention isformed using ATRP techniques and may be found in Han et al., “Synthesisand Characterization of New Liquid-Crystalline Block Copolymers withp-Cyanoazobenzene Moieties and poly(n-butyl acrylate) segments UsingAtom-Transfer Radical Polymerization,” Macromolecules, Vol. 37, pp.9355-9365 (2004):

where m and n are positive numbers indicative of the nominal number ofrepeating units per polymer chain.

Block copolymers having non-LCP polystyrene blocks andmesogen-substituted (meth)acrylate blocks find utility herein and may beprepared by any of a variety of methods including cationicpolymerization of styrene, followed by sequential living ionicpolymerization of the polyacrylate block. Structure I shown below isdescribed in Yamada et al., “Synthesis of Side-Chain Liquid CrystallineHomopolymers and Block Copolymers with Well-Defined Structures by LivingAnionic Polymerization and Their Thermotropic Phase Behavior,”Macromolecules, Vol. 28, pp. 50-58 (1995). Structure II shown below is adiblock polymer having a non-LCP polystyrene block (B) and a methyl(meth)acrylate LCP block (A) modified with a mesogenic side-chain group.This polymer is described in Yamada et al., “Side-Chain LC BlockCopolymers with Well Defined Structures Prepared by Living AnionicPolymerization. 2: Effect of the Glass Transition Temperature ofAmorphous Segments on the Phase Behaviour and Structure of the LCSegment,” High Performance Polymers, Vol. 10(1), pp. 131-138 (1998) andmay be prepared using living ionic polymerization techniques.

Polystyrene-mesogen-substituted acrylate block copolymers can also beprepared using controlled radical reaction schemes such as ATRP,nitroxide-mediated polymerization (NMP) and reverse-addition fragmenttransfer (RAFT). These reactions schemes can involve sequential buildingof each polymer block or building the end blocks simultaneously onto amid-block. Using the first approach, one end of the polymer remainsreactive while using the latter approach involved additionpolymerization of the LCP end-blocks onto a telechelic mid-block whichacts as a difunctional macroinitiator. For example, achloride-terminated polyisobutylene mid-block prepared by cationicpolymerization, can be used as a macroinitiator for mesogen-susbstitutedstyrene or acrylate monomers.

Structures III and IV find utility herein and have been prepared usingcontrolled free radical polymerization techniques. Structure III isdescribed in Barbosa et al., “Living tandem free radical polymerizationof a liquid crystalline monomer,” Polymer Bulletin, Vol. 41, pp. 15-20(1998) and was prepared using NMP techniques. Structure IV shown belowis a diblock polymer having a non-LCP polystyrene block (B) and an LCPblock (A) of poly(methyl methacrylate) bearing a chiral diphenyl estermesogenic unit lined in to the backbone by a dodecyloxy spacer. Thismolecule can be formed by ATRP as described in Hamley et al., “Interplaybetween Smectic Ordering and Microphase Separation in a Series ofSide-Group Liquid-Crystal Block Copolymers,” Macromolecules, Vol. 37,pp. 4798-4807 (2004).

where m and n are positive numbers indicative of the starting of therespective monomers employed in the synthesis of the polymer.

Another example of a block copolymer having non-LCP polystyrenemidblocks and LCP endblocks formed with (meth)acrylate monomers modifiedwith mesogens of a similar structure to that shown above and also formedby ATRP techniques is the following structure V and is described in Tianet al., “Photocrosslinkable Liquid-Crystalline Block Copolymers withCoumarin Units Synthesized with Atom Transfer Radical Polymerization,”Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 41, pp.2197-2206 (2003):

Where m and n are positive numbers indicative of the nominal number ofrepeating units per polymer chain.

Other examples of LC block copolymers having LCP blocks formed with(meth)acrylate repeating units are disclosed in Hao et al., “Molecularcomposite materials formed from block copolymers containing a side-chainliquid crystalline segment and an amorphous styrene-alt-maleic anhydridesegment,” Polymer, Vol. 45, pp. 7401-7415 (2004). An example given byHao et al. is an LC block copolymer formed with apoly[6-[4-4′-methoxyphenyl)phenoxy]hexyl methacrylate] segment (PMM-LC)and a styrene-co-maleic anhydride segment (alternating structure) andmay be prepared using RAFT techniques. The reaction to produce PMM-LC isshown below:

This polymer can then be used to re-initiate styrene/maleic anhydridealternating copolymerization.

Block copolymers having non-LCP polystyrene blocks with the B blocksformed from repeating units other than (meth)acrylate monomers may alsobe employed herein. For example, see Wan et al., “Nitroxide-mediated‘living’ free radical synthesis of novel rod-coil diblock copolymerswith polystyrene and mesogen-jacketed liquid crystal polymer segments,”Polymer International, Vol. 49, pp. 243-247 (2000) wherein an example ofa block copolymer having a non-LCP polystyrene block ispolystyrene-block-poly{2,5-bis[4-methoxyphenyl)oxycarbonyl]styrene}These polymers are formed using NMP techniques.

LCP blocks having non-LCP polystyrene blocks with a LCP block formedwith siloxane repeating units may be employed herein. One example iscyclic trimethyltrivinyltrisiloxane which is modified with mesogenicside groups. For example, in Moment et al., “Synthesis ofpolystyrene-polysiloxane side-chain liquid crystalline blockcopolymers,” Macromolecular Rapid Communications, Vol. 19, pages 573-579(1998), mesogens are attached to the siloxane backbone of apolystyrene-polysiloxane side-chain liquid crystal block copolymerfollowing synthesis of the block copolymer. The mesogens may have thefollowing structures:

The following polydimethylsiloxane LCP block copolymer also findsutility herein and can be formed using ATRP techniques:

where m and n are positive numbers indicative of the starting ratios ofthe respective monomers employed in the synthesis of the polymer. SeeHuan et al., “Synthesis and Properties ofPolydimethylsiloxane-Containing Block Copolymers via Living RadicalPolymerization,” Journal of Polymer Science: Part A: Polymer Chemistry,Vol. 39, pp. 1833-1842 (2001).

Polymers formed of repeating units of epichlorohydrin wherein theepichlorohydrin is modified with a mesogenic group may be employed inthe formation of the LCP block copolymers disclosed herein.Epichlorohydrin polymers are formed using a ring opening polymerizationof epichlorohydrin, followed by subsequent substitution of the chloridewith a mesogenic group, for example, —CH₂O(CH₂)_(n)OArAr—N.Epichlorohydrin monomers can then be added using living ionicpolymerization techniques to obtain the LCP block copolymer. See X. Hanet al. at 743 for the formation of side-chain liquid crystalpoly[1-({[4-cyano-4′-diphenyl)oxy]alkyl}oxy)2,3-epoxypropane] which maybe employed as the mesogenic A block in an embodiment of the presentinvention. Such a polymer may be represented by the formula:

where X and Y are integers. X. Han et al., “Synthesis andCharacterization of Side-Chain Liquid CrystallinePoly[1-({[4-cyano-4′-diphenyl)oxy]alkyl}oxy)2,3-epoxypropane],”Macromolecular Chemistry and Physics at 743-751. See also M. C. Bignozziet al., “Liquid Crystal Poly(glycidyl ether)s by Anionic Polymerizationand Polymer-Analogous Reaction,” Polymer Journal, Vol. 31, No. 11-1, pp.913-919 (1999) wherein the mesogenic group has the structure—OArN═NArO(CH₂)_(m)CH₃. Such polymers can also be prepared by asequential ring-opening anionic polymerization of different epoxides oneof which has a mesogneic side chain group.

LCP block copolymers having substituted non-LCP polyamide blocks andblocks formed with mesogen-substituted amide repeating units with thefollowing structure can also be prepared via ring opening anionicpolymerization:

See C. Guillermain et al., “Homopolymer and copolymers ofN^(ε)-4-phenylbenzamido-L-lysine and N^(ε)-trifluroracetyl-L-lysine:Synthesis and liquid-crystalline properties,” Macromolecular Chemistryand Physics, Vol. 203, Issue 10-22, pp. 1346-1356 (2002).

Ionic polymerization techniques lend themselves to the addition of avariety of different monomers to living ionic polymerizations as well.LCP monomer units can be added sequentially to living ionicpolymerizations reactions, thereby readily building LCP blocks ontonon-LCP midblock. For example, mesogen-substituted monomers such asacrylates as discussed above, and styrenic monomers, may also be used ina sequential cationic polymerization scheme to yield the desired LCPblock copolymer.

Examples of cationically prepared LCP monomer units which can besequentially added to living ionic polymerizations include, for example,cyclic structures such as 2-methyl-7-oxa-bicyclo[2,2,1]heptane, andpolyoxazolines such as those having the following general structure:

See Rodriguez-Parada et al., “Synthesis and Characterization of LiquidCrystalline Poly(N-acelyethyleneimine)s,” Journal of Polymer Science:Part A, Polymer Chemistry, Vol. 25, 2269-2279 (1987).

Mesogen substituted isocyanates having the following general structurecan be polymerized cationically and subsequently added to a non-LCPblock of polyisoprene via sequential ionomeric addition:

See Jun-Hwan Ahn et al., “Synthesis of well-defined block copolymers ofn-hexyl isocyanate with isoprene by living anionic polymerization,”Polymer 44, pp. 3847-3854 (2003).

Mesogen substituted styrene monomers having the following generalstructure can be employed to prepare an LCP A block via cationicpolymerization techniques which can then be subsequently added to anon-LCP block via sequential ionomeric addition:

In the block copolymers employed in the invention, the B block may bealiphatic or aromatic. The B block may be formed with any of a varietyof suitable repeating units including, but not limited to, olefins,esters, ethers, amides, and siloxane repeating units, for example.

In some embodiments, the B block is aliphatic. In these embodiments,suitably, the B block has less than 10% aromaticity by weight of the Bblock, more suitably the B block has less than 5% aromaticity by weightof the B block, and most suitably the B block has substantially noaromaticity. This type of block may be a soft block.

In some embodiments, the B block is aromatic. See for example, Gomes etal. at 713 wherein the B or mid block is polystyrene.

Styrenic block copolymers having styrene end-blocks and diene midblockssuch as isoprene or butadiene, can be modified with mesogenic sidechains to form a liquid crystal block copolymer wherein polystyrene isthe non-LCP B block. The styrene-diene block polymers can be synthesizedusing any known method followed by addition of the mesogenic side chain.Examples are found in Mao et al., “Molecular Design, Synthesis, andCharacterization of Liquid Crystal-Coil Diblock copolymers withAzobenzene Side Groups, Macromolecules,” Volume 30, pages 2556-2567(1997), carboxylic acid functionalized azobenzene mesogenic side chainswere attached to the isoprene block. One example has the structureHOOC(CH₅)OArN═NArC≡N. The mesogen was attached via acid chloridecoupling by converting the carboxylic acid to the acid chloride, oxalylchloride prior to addition to the isoprene block in order to improvereaction times. Hydroboration was used to convert pendent double bondsof an isoprene block to hydroxyl groups to which the mesogenic groupswere attached via acid chloride coupling.

Modified styrene monomers may be employed for both the formation of thenon-LCP block (B) and the LCP block (A). For example, an acetoxystyrenepolymer forms the basis for the following LCP block copolymer formed byliving free radical polymerization:

where M and N are integers. See Bignozzi et al., “Liquid crystallineside chain-coil diblock copolymers by living free radicalpolymerization,” Macromolecular Rapid Communications Vol. 20, pp.622-627 (1999).

Another example of a block copolymer of styrene and isoprene modifiedwith mesogen side-chain groups is described in J. Wang et al., “LiquidCrystalline, Semifluorinated Side Group Block Copolymers with Stable Lowenergy Surfaces: Synthesis, Liquid Crystalline Structure, and CriticalSurface Tension,” Macromolecules, Vol. 30, pp. 1906-1914 (1997).Poly(styrene-b-1,2/3,4-isoprene is first synthesized by anionicpolymerization techniques. The base block polymer was hydroboratedfollowed by attachment of semi-fluorinated side groups by formation ofester linkages between the hydroxy groups and the semifluorinated acidchloride. The block copolymer has the following structure:

The length of the fluorocarbon side chain determines the ability of thepolymer to form a micellular structure. More than six —(CF₂)— groupswere found to produce micelle structures. Suitably ten fluorocarbongroups are present in the mesogenic side chain for substantially all ofthe molecules to form a micellular structure. The length of themethylene spacer group was also found to affect micelle formation. Withthree methylene groups in the spacer, about 80% of the molecules formedmicelles. With —(CH₂)₅— about 30% of the molecules formed micelles andwith —(CH₂)₉— only 20% of the molecules. A sufficiently long spacergroup improves the solubility of such molecules in solvent. See Wang etal. at page 1909-1910.

(Meth)acrylate block copolymers modified with fluorocarbon side-chainmesogenic groups find utility herein and may be formed using ATRP asdescribed in Al-Hussein et al., “Nanoordering of Fluorinated Side-ChainLiquid Crystalline/Amorphous Diblock Copolymers, Macromolecules,” Vol.38, pp. 9610-9618 (2005). These polymers have the following structure:

These types of LCP block copolymers also provide a surface having a lowsurface energy or low coefficient of friction and therefore find utilityin also providing lubricity to the medical device. They may be used inthe matrix material which forms at least a portion of the blockcopolymer, or they may also find utility as a coating on the surface(s)of a device.

Multiarm star rod-coil block copolymers may be employed herein. Forexample, see Chen et al., “Synthesis and Characterization of NovelMesogen-Jacketed Liquid Crystalline Miktoarm Star Rod-Coil BlockCopolymer,” Macromolecular Rapid Communications, Vol. 27, pp. 51-56(2006). These multiarm star block copolymers were produced by ATRP ofstyrene monomers and {2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene}rigid rod segments. Both three arm rigid rod block copolymers (Chen etal. at 51-56) and four arm rigid rod block copolymers of this type maybe employed. See Wang et al., “Synthesis and characterization offour-armed star mesogenjacketed liquid crystal polymer,” Journal ofPolymer Science. Part A: Polymer Chemistry, Vol. 43, pp. 733-741 (2005)for a four armed structure. Also reproduced in Polymer, Vol. 45, pp.3637-3642 (2004).

Another example of a multiarm star block copolymer is a tri-armed starpoly(ε-caprolactone)-b-poly {2,5-bis[(4-methoxyphenyl) oxycarbonyl]styrene} [S-(PCL-b-PMPCS)₃]. Shi et al., “Synthesis and Characterizationof a novel star shaped Rod-Coil Block Copolymer,” Polymer Bulletin, Vol.52, pp. 401-408 (2004). Different initiators may be employed such as1,3,5-(2′-bromo-2′-methylpropionato)benzene and1,1,1-tris(2-bormo-isobutyryloxymethyl)propane. See Wang et al.,“Synthesis of a novel star liquid crystal polymer using trifunctionalinitiator via atom transfer radical polymerization,” European PolymerJournal, Vol. 41, pp. 933-940 (2005). Other examples of star blockcopolymers which may be employed herein are described in He et al.,“Synthesis of novel multi-arm star azobenzene side-chain liquidcrystalline copolymers with a hyperbranched core,” European PolymerJournal, Vol. 40, pp. 1759-1765 (2004) and He et al. “BranchedAzobenzene Side-Chain Liquid-Crystalline Copolymers Obtained bySelf-Condensing ATR Copolymerization,” Macromolecular RapidCommunications, Vol. 25, pp. 949-953 (2004). The multi-arm blockcopolymers can be synthesized using ATRP techniques using amulti-functional hyperbranched polyether prepared frompoly(3-ethyl-3-(hydroxymethyl)oxetane)(PEHO) and2-bromo-2-methylproponyl bromide. The liquid crystalline arms werepoly[6-(4-methoxy-4″-oxy-azobenzene)hexyl methacrylate].

Multiarm block copolymers may be formed living free radicalpolymerizations as discussed above, as well as anionic and cationicpolymerizations, end-coupling of prepolymers or a combination ofstrategies.

The B block may also be formed with hydrophilic monomer units. Examplesof suitably hydrophilic monomers include, but are not limited to, shortchain aliphatic ethers such as polyethylene oxide or polyethyleneglycol, polytetramethylene oxide or polytetramethylene glycol diols ordicarboxylic acids containing a metal sulfonate group, oligomers such aspolyalkylene glycol copolymerized with other monomers such as aliphaticdicarboxylic acids, hydrophilic acrylates available from Sartomer suchas polyethylene glycol diacrylate, acrylamides andN,N-dimethylacrylamide, N-vinylpyrrolidone, etc.

An example of an LCP block copolymer having a hydrophilic B block isdescribed in He et al., “Synthesis of side-chain liquid-crystallinehomopolymers and triblock copolymers with p-methoxyazobenzene moietiesand poly(ethylene glycol) as coil segments by atom transfer radicalpolymerization and their thermotropic behavior,” Journal of PolymerScience Part A: Polymer Chemistry, Vol. 41, Issue 18, pages 2854-2864(2003). Triblock copolymers, A-B-A, wherein the A block is formed ofrepeating units of an azobenzene monomer, 6-(4-methoxy-azobenzene-4′oxy)hexyl methacrylate and the B block is formed of repeating units ofpolyethylene glycol were synthesized using atom transfer radialpolymerization (ATRP). See also He et al., “Synthesis of Side ChainLiquid Crystal-Coil Diblock Copolymers with p-Methoxyazobenzene SideGroups by Atom-Transfer Radical Polymerization (structure V)”, PolymerChemistry, Vol. 41, 2854-2864 (2003) and Tian et al., “Synthesis,Nanostructures, and Functionality of Amphiphilic Liquid CrystallineBlock Copolymers with Azobenzene Moieties,” Macromolecules, Vol. 35, pp.3739-3747 (2002) (structure VI) below:

Another example is poly(11-(4′-cyanophenyl-4″-phenoxy)undecylmethacrylate) with polyethylene glycol segments. See He et al.,“Synthesis of side group liquid crystal-coil triblock copolymers withcyanodiphenyl moieties and PEG as coil segments by atom-transfer radicalpolymerization and their thermotropic phase behavior,” Polymer Bulletin,Vol. 48, pp. 337-344 (2002).

The above are intended for illustrative purposes only, and not as alimitation on the scope of the present invention.

The A block may have anywhere from about 2 to about 50 repeating units,and more suitably about 2 to about 25 repeating units, and the B blockmay have anywhere from about 2 to about 25 repeating units, and suitablyabout 2 to about 10 repeating units.

In some embodiments the block copolymer further has a C block, the Cblock is a mesogenic block different than the mesogenic A block. Themesogenic units of the C block may be selected from those mesogenicrepeating units discussed as useful in forming the A block. However, ina liquid crystal polymer having both an A block and a C block, the Cblock is formed from different mesogenic repeating units than those ofthe A block. For example, in one embodiment, the A block of the liquidcrystal block copolymer is a polyamide segment and the C block is apolyester segment formed using aromatic hydroxycarboxylic acids, forexample. Examples of suitable mesogenic units for formation of thepolyamide A block structure include, for example,

This portion of the liquid crystal block copolymer can be made by thecondensation reaction between HOOC—AR—COOH (benzene-1,4-dicarboxylicacid) and H₂N—AR—NH₂ (1,4-diaminobenzene) to form the followingstructure:

In this embodiment, suitable B blocks may be formed by condensation ofhexanedioic acid and hexamethylenediamine (nylon 6,6), ring openingpolymerization of caprolactam (nylon 6) or ring opening polymerizationof laurolactam (nylon 12), for example.

Nylon 6 (polycaprolactam) is not a condensation polymer, but rather isformed by the ring opening polymerization of caprolactam monomers.

Nylon 6,6, on the other hand, is formed by condensation betweenhexanedioic acid (adipic acid) and 1,6-diaminohexane(hexamethylenediamine): repeating unit:

H₂N(CH₂)₆NH₂+HOOC(CH₂)₄COOH→[—NH—(CH2)₆—NH—CO(CH2)₄—CO—]_(n)+H₂O

Hexanedioyl dichloride may be used in place of hexanedioic acid.

The above list is intended for illustrative purposes only, and not as alimitation on the scope of the present invention.

The liquid crystal polyester A block, the nylon B block and the liquidcrystal polyamide C block can be connected via conventional condensationreactions.

The C block may also have anywhere from about 2 to about 50 repeatingunits, and more suitably anywhere from about 2 to about 25 repeatingunits.

In some embodiments, the A block is from about 30% to about 95%, moresuitably about 50% to about 95%, and even more suitably about 70% toabout 90%, by weight of the block copolymer and the B block is about 5%to about 70% by weight of the block copolymer, and more suitably fromabout 5% to about 50% by weight of the block copolymer, more suitably,the B block is about 10% to about 30% by weight of the block copolymer.In some embodiments, the B block or soft segment is about 10% or less byweight of the LC block copolymer.

Any suitable method of polymerization may be employed depending on themonomers, oligomers, or polymers which are employed. Most commonly, thepolymerization can be accomplished via condensation reactions which areachieved through reacting molecules incorporating alcohol, amine orcarboxylic acid (or other derivative) functional groups. An ether,amide, or ester linkage is formed and a small molecule, commonly water,is released. Thus, only a part of the monomer becomes part of thepolymer.

EXAMPLE

In a specific example 4-hydroxy-2-benzoic acid (HBA) may be acetylizedto 4-acetoxybenzoic acid (ABA) with acetic anhydride as the solvent inthe presence of a catalytic amount of sodium acetate in the manner ofChen et al, “Synthesis and properties of liquid crystalline polymerswith low T_(m) and broad mesophase temperature ranges,” Polymer, 46(2005) 8624-8633. Still following the method of Chen et al, ABA then maybe reacted with 1,4-butanediol (BDO) in a molar ratio of about 1:3 andSb₂O₃ catalyst in an amount of about 300 ppm to produce the esterABA-BDO-ABA.

Polymerization is then accomplished by adding a mixture of the esterABA-TMG-ABA, terephthalic acid (TPA), a nylon 6 polymer terminated onboth ends with acid groups (Ny6) and 250-300 ppm of Sb₂O₃ or Ti(OBu)₄catalysts to a flask with a nitrogen purge using a molar ratio of theester to TPA to Ny6 dicarboxylic acid of 1.0:0.67:0.33. The nitrogenoutlet is equipped with a distillation column with vacuum. The mixtureis heated at melt for about 5 hours at a temperature of about 200° C. toabout 250° C., depending on the temperature necessary to melt themixture. Thermal stabilizers and antioxidants such as Irganox® 1010available from Ciba-Geigy are used added to inhibit decomposition. Themixture is stirred, for instance at 200 rpm once the melt temperaturehas been reached. The nitrogen flow is regulated to prevent evaporationof reactants. After about 3-5 hours the temperature is graduallyincreased to about 280° C. and the acetic acid produced by condensationis removed by distillation. When no more distillate is observed a vacuumof about 10 torr is applied for 2-3 hours and then the vaccuum isreduced to 1-2 torr and the mixture stirred continuously for anadditional 4 hrs, all the while maintaining the temperature at about280° C. The product is then allowed to cool. Monomers and oligomers maybe removed by Soxhlet extraction using acetone.

The resultant polymer is an A-B-A block copolymer having a structure of[(ABA-BDO-ABA-TPA)_(x)ABA-BDO-ABA]-Ny6-[ABA-BDO-ABA-(TPA-ABA-BDO-ABA)_(y)].

In modifications of the above equivalent amounts of ethylene glycol or1,3 propane diol may be substituted for 1,4-butanediol,6-hydroxy-2-naphthoic acid may be substituted for 4-hydroxy benzoicacid, 2,6-naphthalene dicarboxylic acid may be substituted for TPA,and/or other diacid terminated nylon polymers such as nylon 6,10 ornylon 9,12, may be substituted for the nylon 6 polymer. An A-B diblockcopolymer may be synthesized in a similar manner using a mono-acidterminated nylon polymer such as nylon 12, in place of the nylon 6diacid. Furthermore the relative ratio of short diacid to acidterminated nylon can be varied over a very wide range for instance fromabout 1:10 to about 1:10 on an acid equivalents basis.

The liquid crystal block copolymer of the invention may itself beemployed in the formation of medical devices or components thereof, or,the liquid crystal block copolymer may be blended with another polymeror polymers. In the latter case, suitably, the polymer and the B blockmay be selected so as to be compatible with one another. Compatibility,as used herein, refers to compatibility on both the macroscopic andmicroscopic, i.e. molecular, scale. Thus, compatibility on a macroscopicscale, may refer to those polymer blends which do not exhibit grossphase separation.

In polymer mixtures, the matrix polymer may interact strongly with theLC block copolymer or one block of the LC block copolymer, thusproviding desirable polymer properties.

In mixtures wherein the LC block copolymer is blended with otherpolymers, at least one other polymer of the blend, may be selected fromthose polymers which are non-liquid crystal polymers. Examples ofsuitable polymers which may be used for blending with the LC blockcopolymer described herein include, but are not limited to, polyestersand copolyesters, polyamides, polyethers, polyimides, polyolefins andsilicones, for example. These polymers are intended for illustrativepurposes only, and not as a limitation on the scope of the presentinvention.

Specific examples of suitable polymers which may be employed in a blendinclude polyamide elastomers such as those sold under the tradename ofPEBAX® available from Arkema, headquarters in Paris, France, andpolyester elastomers such as those sold under the name of HYTREL®available from DuPont in Dover, Del. are also suitable for use.

For example, if the liquid crystal block copolymer is blended with apoly(ether-block-amide) copolymer having an (AB)_(n) block copolymerstructure wherein the A block is nylon and the B block ispolytetramethylene oxide, a suitable LC block copolymer B block mayinclude amide repeating units or a polytetramethylene oxide structure.The block may suitably be less than about 50% by weight of the LC blockcopolymer, more suitably about 30% by weight or less of the LC blockcopolymer and most suitably about 10% by weight or less of the LC blockcopolymer.

The tensile strength of a typical poly(ether-block-amide) thermoplasticelastomer of the type described above has tensile strength of about10,000 psi and DSC melting point of about 174° C.

Suitably, the LC block copolymer, to act as a reinforcing material insuch a polymer blend, has a tensile strength of greater than about10,000 psi, for example, greater than about 12,000 psi, more suitablygreater than about 20,000 psi and most suitably greater than about30,000 psi.

Thus, it is desirable to select the LC block copolymer structure so thatit has a strong interaction with the thermoplastic elastomer to achievemechanical strength enhancement through effective load/forcetransferring.

It is also desirable that the LC block copolymer have a melting pointwithin a thermoplastic processing window of less than the thermaldegradation temperature of the thermoplastic elastomer. In the casewhere the thermoplastic elastomer is poly(ether-block-amide), forexample, the melting point range is suitably less than about 240° C.Extrusion/coextrusion is an example of a suitable method to process suchthermoplastic materials.

The above example is intended for illustrative purposes only, and not asa limitation on the scope of the invention. Other polymers are known tothose of skill in the art and may also be employed herein.

If a blend of polymers is employed, the amount of LC block copolymer issuitably about 75% or less and more suitably about 50% or less. Theamount of LC block copolymer employed may be from about 5% to about 75%and more suitably about 5% to about 50% and even more suitably about 10%to about 30%.

The at least one second polymer or blend of polymers may be employedfrom about 25% to about 95%, more suitably about 50% to about 95% andeven more suitably about 70% to about 90%.

The present compositions may be employed in the manufacture of anymedical device or component thereof which is suitably formed frompolymer compositions. Examples include catheter assemblies used indiagnosing and treating diseases such as vascular diseases.

The present invention finds utility in the manufacture of expandablemedical balloons, particularly those employed in the cardiovascularsystem wherein the balloon size is very small.

Balloon formation is known in the art. In some processes, a tube ofpolymer material is extruded and then expanded radially and axially.Balloon formation is described in U.S. Pat. No. 4,490,421 and incommonly assigned U.S. Pat. No. 6,024,722, both of which areincorporated by reference herein in their entirety. Of course, otherprocesses are known and may be employed in the present invention.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the attached claims. Thosefamiliar with the art may recognize other equivalents to the specificembodiments described herein which equivalents are also intended to beencompassed by the claims attached hereto.

1. A medical device, at least a portion of said device formed from a polymer composition comprising at least one liquid crystal block copolymer having at least one A block and at least one B block and wherein the A block is a liquid crystal polymer block formed from repeating units comprising mesogenic groups; and the B block is a non-liquid crystal polymer block.
 2. The medical device of claim 1 wherein the liquid crystal block copolymer is selected from the group consisting of those polymers having the general formula A-B diblock, (A-B)_(n) wherein n is 1 to 20, A(B-A)_(n) where n is 2 to 20, B(A-B)_(n) where n is 2 to 20, A-B-A triblock, B-A-B triblock, A-B-A-B-A pentablock, multiblock copolymers, linear tetrablock copolymers, random block copolymers and random alternating block copolymers, radial star block copolymers, H-type branched block copolymers, T-type branched block copolymers, combs, brushes, dendrons and mixtures thereof.
 3. The medical device of claim 1 wherein said block copolymer further comprises a mesogenic block C different than the A block and said block copolymer has a structure which is selected from the group consisting of B-(A-B-C)_(n)-B wherein n is 3 to 20, A-B-C triblock, A-C-B triblock, and A-B-C random block.
 4. The medical device of claim 1 wherein said mesogenic groups comprise at least two aromatic rings.
 5. The medical device of claim 1 wherein said mesogenic groups comprise fluorinated side-chain groups of at least —(CF)₈—
 6. The medical device of claim 4 wherein said —(CF)₈— is connected to a spacer having three methylene groups or less.
 7. The medical device of claim 1 wherein said B block is aromatic.
 8. The medical device of claim 7 wherein said B block is styrene.
 9. The medical device of claim 1 wherein said A block is formed from repeating units wherein the repeating unit comprises a monomer selected from the group consisting of siloxanes, (meth)acrylates, isocyanates, styrenic monomers, and diene monomers.
 10. The medical device of claim 9 wherein said monomer comprises side chain mesogenic groups.
 11. The medical device of claim 1 wherein the A block is formed from repeating units wherein the repeating units comprises a (meth)acrylate monomer modified with mesogenic side chain groups and the B block comprises styrene.
 12. The medical device of claim 1 wherein the polymer composition further comprises at least one polymer selected from the group consisting of polyamides, polyesters, polyethers, polyolefins, polyimides, block copolymers comprising at least one polyolefin, polyester, polyether, polyamide, and/or polyimide segment, silicones, and mixtures thereof and mixtures thereof.
 13. The medical device of claim 1 wherein said liquid crystal block copolymer comprises about 50% to about 95% by weight of said A block and about 5% to about 50% by weight of said B block.
 14. The medical device of claim 1 wherein said medical device is a catheter assembly comprising at least one shaft or shaft assembly, and said at least a portion of said medical device formed from said polymer composition is said at least one shaft or shaft assembly.
 15. The medical device of claim 1 wherein the medical device is an inflatable medical balloon.
 16. The medical device of claim 15 wherein said balloon is mounted on a catheter.
 17. The medical device of claim 15 further in combination with a stent.
 18. The medical device of claim 1 wherein said block copolymer further includes a C block, the C block comprises mesogenic repeating units, the mesogenic repeating units are different than those of the A block.
 19. A medical device, at least a portion of said device formed from a polymer composition, the polymer composition comprising: at least one liquid crystal block copolymer having at least one A block and at least one B block wherein the A block is a liquid crystal polymer block formed from repeating units comprising mesogenic groups and the B block is a non-liquid crystal polymer block; and at least one polymer which is compatible with said B block of said liquid crystal block copolymer.
 20. The medical device of claim 19 wherein the liquid crystal block copolymer is selected from the group consisting of those polymers having the general formula A-B diblock, (A-B)_(n) wherein n is 1 to 20, A(B-A)_(n) where n is 2 to 20, B(A-B)_(n) where n is 2 to 20, A-B-A triblock, B-A-B triblock, A-B-A-B-A pentablock, multiblock copolymers, linear tetrablock copolymers, random block copolymers and random alternating block copolymers, radial star block copolymers, H-type branched block copolymers, T-type branched block copolymers, combs, brushes, dendrons and mixtures thereof.
 21. The medical device of claim 19 wherein said mesogenic group comprises at least two aromatic rings.
 22. The medical device of claim 19 wherein said B block is aromatic.
 23. The medical device of claim 19 wherein said A block is formed from monomer units wherein the base monomer unit is selected from the group consisting of siloxanes, (meth)acrylates, isocyanates, styrenic monomers, and diene monomers.
 24. The medical device of claim 23 wherein said base monomer comprises side chain mesogenic groups.
 25. The medical device of claim 19 wherein said device is a catheter assembly.
 26. The medical device of claim 25 wherein said at least a portion of said medical device is a balloon mounted on said catheter assembly. 